Flat panel display devices can include liquid crystal displays (LCD), plasma display panels (PDP), organic light emitting displays (OLED), field effect displays (FED), electrophoretic displays (EPD), and electrowetting displays (EWD).
Among these types of displays, the electrowetting display device expresses gradation in pixels by controlling movement of oil in water, with water being an electrolyte. Since the electrowetting display device is a shutter type display device that does not use a polarizing plate, an EWD has high light transmittance with gamma characteristics (measured by voltage) that are linear. In addition, the electrowetting display devices can be formed as a reflective type display or transmission type display according to the environment of application. A reflective type of electrowetting display device may omit back light.
While electrowetting display devices are manufactured using the same processes as those used to manufacture other flat panel display devices, such as LCDs, for example, an additional filling process is required to fill water and oil over the device. For proper operation of an electrowetting display device, the layer below the oil must be a water repellent layer having a hydrophobic property. It is difficult to form a hydrophilic layer, like a partition layer, over the water repellent layer. To form a partitioning wall, the water repellent layer must be applied with a reactive ion etching (RIE) treatment to provide hydrophilicity. After forming the partition walls, oil is provided, and then a thermal reflow process is applied so that the water repellent layer resumes hydrophobicity to operate the electrowetting display device.
As described above, a plurality of processes have to be conducted alternately to provide hydrophilicity and hydrophobicity, which results in a complicated process, increased time and increased cost. Further, the water repellent layer after thermal reflow process may fail to acquire sufficient hydrophobicity which can lead to poor oil filling and deteriorated performance of the electrowetting display devices.